The life cycle of C. difficile begins in the spore form. These spores are easily transmitted as they are resistant to heat, acid, and antibiotics. The spores can remain viable for months outside of the human body. In the hospital, they can be found on bedding, furniture, medical equipment, as well as on the skin and jewelry of caregivers.8 Once ingested, the spores pass through the upper digestive tract into the intestines where they can germinate and colonize the colon. A study showed that 21% of patients receiving antibiotics and admitted to a general medical ward were colonized by this bacterium.9 Healthy individuals are usually protected from CDI by the normal bacterial flora of the gut, which resists C. difficile’s colonization and growth. Disruption of the normal microflora by antibiotics allows C. difficile to proliferate, produce toxins, and cause disease.10 C. difficile induces diarrhea and colitis through the release of two protein exotoxins, toxin A and toxin B. Greater than 60% of the population has serum and colonic antibody responses to these toxins.11,12 Low or absent concentrations of serum IgG antibody against C. difficile toxins has been shown to confer a greater risk of CDI among hospitalized patients who become colonized by this bacterium.13 Toxigenic C. difficile can be identified in more than 95% of pseudomembranous colitis cases and in 15%–25% of antibiotic-associated diarrhea cases.14,15
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The role of probiotics in the prevention of C. difficile remains unclear.60,61 There are many studies in the literature regarding probiotics in the prevention of antibiotic-associated diarrhea, but fewer studies looking at probiotics in the prevention of CDI. In 2004, Plummer et al reported a double-blind, placebo-controlled trial examining the role of probiotics (Lactobacillus and Bifidobacterium) in the prevention of CDI.62 In this study, 150 consecutive patients receiving antibiotic therapy were randomized to receiving the probiotic or placebo. The results showed that, on the basis of developing diarrhea, only 2.9% of stool samples in the probiotic group were positive for C. difficile-associated toxins versus 7.25% in the placebo-controlled group. Despite this finding, the total number of patients who tested positive for C. difficile was actually higher in the probiotic group (n = 11) than in the placebo group (n = 9), so the effect of the probiotic in this study is uncertain. S. boulardii does not appear to be effective in primary prevention of CDI.33,63 At this time, there is insufficient evidence to support the widespread use of probiotics for the primary prevention of CDI. Larger randomized control trials are needed to support its use.
